On Mon, Feb 28, 2011 at 8:27 PM, Matthew <mattinker@yahoo.com> wrote:
>
>
> Hi Dave,
>
> thank you for the information on extruded alloys. I know that I got the
> idea the extrusions were close to pure Al from the net when I started
> casting Al. This seemed to be backed up by the gumminess of the metal when
> turning. I thought that the difference was that extrusions are stretched
> after they are extruded which hardens them. I visited an aluminium factory
> in the south of France where I did a course in Aluminium "joinery" making
> windows and doors. Large hot slugs of Al were fed into the extruding
> machine, and an enormous hydraulic ram forced the hot short Al through the
> forms in lengths of 100 meters at high speed. The newly extruded profile was
> then stretched which made it rigid and straight. I no longer have the doc
> and that they gave me, but it must have had the type of alloy that they
> used.
>
> How about a Junk-yard scrap non ferrous metal file to get al this kind of
> information together?
>
> I have "Junkyard Steels" from anvillefire that I shall put in a file.
>
> Thanks again, Matthew
>
> --- In gingery_machines@yahoogroups.com, David Patterson <odd_kins@...>
> wrote:
> >
> > I'm not sure where the myth was started that extruded aluminum is near
> pure aluminum and is no good for casting. But:
> > Â
> > % of materials
> > 6061-t6
> > 95.8 - 98.6 aluminum
> > .80 - 1.2 magnezium
> > .40 - .80 silicon
> > the rest is other materials
> > Â
> > 7075-t6
> > 87.1 - 91.4 aluminum
> > 2.10 - 2.90 magnezium
> > 1.2 - 2.0 copper
> > 5.1 - 6.1 zinc
> > the rest is other materials, This material cannot be welded, as far as I
> know.
> > Â
> > 356 sand casting alloy
> > 90.1 - 93.3 aluminum
> > 6.5 - 7.5 silicon
> > <= .25 copper
> > .20 - .45 magnezium
> > Â
> > 6061-t6 is used a lot in window frames. Adding copper to this alloy makes
> it more like 7075, which could be bad, If you needed to weld the
> casting.  Adding copper to 7075 you get ?????
> > the high silicon content in 356 is to make it flow better into a mold.
> 356 die casting alloy is slightly different. Magnezium is added to extruded
> alloys to allow it to work harden.
> > Â
> > The problem with casting extruded alloys, people expect it to machine
> just like the block it originally came from. Won't happen, you just took T6
> material to T0 material. This needs to be brought back by heat treating, in
> some fashion. The easiest way I know of is to demold within a few minutes
> of pouring, the agitate in a bucket of cold water, or spray with cold water.
> Again keep well away from the furnace when doing this. Thickness of the
> casting will determan how long it takes to demold.
> > Â
> > Â
> >
> > Dave Patterson
> > odd_kins@...
> > http://home.comcast.net/~oddkins/foundry_home.html
> >
> > --- On Mon, 2/28/11, Matthew Tinker <mattinker@...> wrote:
> >
> >
> > From: Matthew Tinker <mattinker@...>
> > Subject: Re: [gingery_machines] Re: New Here
> > To: gingery_machines@yahoogroups.com
> > Date: Monday, February 28, 2011, 8:05 AM
> >
> >
> > Â
> >
> >
> >
> > David,
> >
> > A couple of things I don't agree with. The only problem with the Zinc
> based alloys is corrosion. Unfortunately, this excellent range of alloys has
> a bad press because it is frequently under- designed to minimise costs and
> therefore breaks. The ZA 12 is great, 11% Al, 1% Cu, and the remaining 88%
> Zn, percentages are by weight. This alloy has characteristics similar to
> cast iron, it is an excellent structural material with good vibration
> damping. This alloy is also very good for bearing surfaces. To cap it all,
> it is a "dream to machine"!
> >
> > Aluminium extrusions are a good source of "pure" Al for making the ZA
> alloys or to make a harder Al alloy, add 5% of copper. It is surprising, but
> molten Al is sufficiently corrosive to dissolve the Cu without having to
> reach it's melting point.
> >
> > WARNING, if you take Zn, Zinc over 700°C, it will "smoke" ie. it reaches
> it's boiling point and gives off zinc in the form of vapour, this is not to
> be inhaled! Poison!
> >
> > If you do anything nasty to yourself, I accept no responsibility!
> >
> > Regards, Matthew
> >
> > Matthew TINKER
> >
> > CNC conversion 1944 Colchester Lathe build-up log
> >
> > http://www.cnczone.com/forums/showthread.php?t=35519
> >
> > --- On Mon, 28/2/11, David Frantz <websterindustro@...> wrote:
> >
> > From: David Frantz <websterindustro@...>
> > Subject: Re: [gingery_machines] Re: New Here
> > To: "gingery_machines@yahoogroups.com" <gingery_machines@yahoogroups.com
> >
> > Cc: "gingery_machines@yahoogroups.com" <gingery_machines@yahoogroups.com
> >
> > Date: Monday, 28 February, 2011, 9:32
> >
> > Â
> >
> > Extruded aluminum NO. Look for originally cast Aluminum as you will
> already have an alloy suitable for casting.
> >
> > As to zinc it is suitable for many machine parts so don't loose any stash
> you may have. What you should avoid is using it for structural parts of the
> lathe. Especially parts where vibration or ringing might be a problem.
> Further don't mix tools used for Aluminum, such as crucibles, with those
> used for zinc.
> >
> > Zinc alloys should be much easier to cast and frankly easier to find. I
> would not avoid using it, it is just a matter of selecting the proper places
> to implement zinc parts. In some places I'd even go so far as to suggest
> that zinc would be a better choice, for example knobs and handles which
> could remain bare. It would avoid that nasty aluminum stain on the hands.
> >
> > One other way to use zinc would be to cast a frame or structure and then
> fill it with epoxy concrete. For a lathe bed this would deaden the frame yet
> give you metal to bolt things like the ways to. So there is more than one
> way to skin a cat here. Adaptation is really the word here; Gingery designed
> a lathe that is ideal for the material, Aluminum in this case, going to zinc
> just requires a bit of thinking or design effort.
> >
> > David A Frantz
> >
> > websterindustro4at4mac.com
> >
> > Sent from my iPhone.
> >
> > On Feb 27, 2011, at 7:57 PM, james <james122964@...> wrote:
> >
> > > So, it would be better to use the extruded aluminum? or should I hunt
> around for actual cast aluminum?
> >
> > >
> >
> > > I sure wish the die cast stuff would have been worth it, as it melts a
> lot easier and is heavier, guess I could use it for pulleys.
> >
> > >
> >
> > > Jim
> >
> > >
> >
> > > --- In gingery_machines@yahoogroups.com, David Frantz
> <websterindustro@> wrote:
> >
> > >>
> >
> > >> Long ago I worked in the die cast industry so I have some experience
> with this. First die cast alloys are not the same as zinc based casting
> alloys designed for sand casting. Second die cast alloys age significantly
> of time. Third die cast alloys are sensitive to the ratios of metals which
> means it is easy to get fining results if the alloy varies from the accepted
> ratios much.
> >
> > >>
> >
> > >> Given that you wouldn't have any problems pouring a Zinc die cast
> alloy. The low melting points mean that you can get by with a cheaper
> furnace. Sources for the alloys where at one time cheap and plentiful
> (carburetor and other auto parts). Zinc die castings can have initial
> strengths equal to similar cast iron parts. So there are good points to
> consider with respect to Zinc castings.
> >
> > >>
> >
> > >> The bad points are also worth considering. One in this context is that
> a Zinc casting might not be as dead as a cast-iron or aluminum one. That is
> you may see much more in the way of ringing and vibration transmission. As
> mentioned above the alloys do age over time which might result in a need to
> re scrape parts overtime. Actually all cast metals have an aging factor it
> is just that some Zinc alloys can age more than others, plus this is in the
> context of die casting.
> >
> > >>
> >
> > >> In the end I would NOT recommend zinc die cast alloys for most parts
> of a lathe. I just think you would get far better results from other
> materials for most of the structure.
> >
> > >>
> >
> > >>
> >
> > >> On the granite:
> >
> > >>
> >
> > >> Granite counter top material can pass as A surface plate. You should
> check the flatness your self and make sure it is well supported to prevent
> bending under use. Simply due to the thickness it ought to be a better
> starting point for a surface plate than ceramic tile or other things that
> are often suggested. In any event realize that a surface plate requires
> maintenance just like every other tool.
> >
> > >>
> >
> > >>
> >
> > >>
> >
> > >> David A Frantz
> >
> > >> websterindustro4at4mac.com
> >
> > >>
> >
> > >
> >
> > >
> >
> > >
> >
> > >
> >
> > > ------------------------------------
> >
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> > [Non-text portions of this message have been removed]
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>
>
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